In the field of communications, a Service Level Agreement (SLA) concerns agreed upon communications service provisioning terms and conditions between a communications services customer making use of communications services provided by a communications service provider. An exemplary SLA may specify communications service provisioning terms including, but not limited to: committed up-link and down-link rates, maximum up-link (and down-link) burst sizes, duration of schedule maintenance down time, availability, etc.
Communications services customers such as, but not limited to: individual users and organizations, negotiate SLAs with communications service providers. Service provider communications networks connect to backbone communications networks and other peer service provider communications networks to participate/provision wide area networked interconnectivity and in so doing negotiate SLAs therebetween.
Besides assessing an end customer's adherence to an SLA to ensure that the end customer adheres to his part of the agreement, a service provider has a duty to, and an interest in, assessing the service provider's own conformance to the customer's SLA to ensure that the service provider adheres to his part of the agreement in provisioning communications services to the end customer. Further, the service provider has an interest in assessing its conformance to SLAs established with backbone communications networks and peer service provider communications networks.
Today, conformance to SLAs is based on post-mortem assessments performed cyclically employing communications-network-attached statistics generator systems, typically at the end of each billing period. Statistics generator systems collect large amounts of content-traffic-related measurement reports, calculate: distributions, averages, means, medians, standard deviations, variances, covariances, etc., therefore generating large amounts of data to be retrieved from the statistics generators for interpretation. Problems with this approach stem from: the necessity for dedicated communications-network-attached statistics generator systems, a content-traffic-related raw measurements reporting bandwidth overhead, a storage overhead at the statistics generator system for tracking information, and archiving), a processing overhead, a statistics retrieval bandwidth overhead, etc. Statistics generator systems are relatively expensive particularly considering that each statistics generator system can only track measurement reports for a limited small number of communications network nodes (typically limited to three communications network nodes); communications network wide solutions requiring the use of large numbers of statistics generators simultaneously and are therefore unscalable.
It is intended that post-mortem assessment information be further used to renegotiate current SLAs, and as a basis for adjusting communication network node parameters possibly leading to infrastructure redeployment. Waiting for a billing cycle to complete, therefore represents a large stumbling block, the mitigation of which, currently includes making contingency provisions (leading to incurred overheads) for, but not limited to: spare bandwidth, spare storage resources, spare processing capacity, etc.
Further related developments include the use of a Network Management System (NMS) managing communication network nodes in a communications network (service provider communications network/backbone communications network). In accordance with a managed communications network deployment scenario, constituent communications network nodes provide raw reporting information derived from measurements to designated statistic generator systems. On a corresponding service cycle, each statistic generator system: extracts SLA-relevant reported measurement values, computes corresponding SLA conformance assessment parameters, and provides the NMS with the SLA conformance assessment parameter reports. The drawbacks of the deployment scenario include, but are not limited to: the necessity of dedicated statistic generator systems, the bandwidth overhead employed in conveying raw traffic measurement reports to statistics generators, the storage overhead in tracking the traffic measurement reports at each statistic generator, the processing overhead in deriving SLA conformance parameters, the bandwidth overhead expended in conveying SLA conformance parameter reports to the NMS, etc. The NMS, and the functions the NMS may provide, are still subject to the service cycles on which the statistics generators operate—end of each billing cycle.
Current developments include the Real Time Flow Monitor (RTFM), an Internet Engineering Task Force (IETF) initiative, Requests For Comments (RFCs) 2720, 2721, 2722, 2723, and 2724: memos discussing issues related to raw traffic flow measurement and raw measurement reporting. Generating and exporting measurements/statistics is an area of active current research within the IEFT Internet Protocol Flow Information eXport (IPFIX) working group. The proposal includes a traffic meter entity which monitors packets, extracts raw packet particulars, and makes a subset thereof available to a meter reader entity. While the proposed meter entity is intended monitor packets at line rate, the meter reader entity is expected to extract the measurements on a predefined schedule. The quantification of network performance is not a purpose of these memos.
The memos assumes that router entities or traffic monitor entities throughout a network are instrumented with meters to inspect traffic. Data reduction in producing requested traffic flow information is suggested to be exercised as near as possible to a traffic measurement point: to minimize the volume of data obtained and transmitted across a network for storage, and to reduce the amount of processing required in traffic flow analysis applications. In order to implement data reduction communications network operators are to be provided with the ability to specify traffic measurement requirements by writing “rule sets” describing what raw traffic specific particulars are to be collected while ignoring the rest. Therefore in accordance with the proposed solution, conformance assessment completeness is sacrificed in favor of reporting overhead savings. Further experimental work is on-going based on these memos.
Another recent development includes a theoretical treatise by J. Y. LeBoulec, and P. Thiran entitled “Network Calculus: A Theory of Deterministic Queuing Systems for the Internet” published by Springer Verlag as Lecture Notes in Computer Science No. 2050 and ISBN 3-540-42184-X. The theoretical investigation into communications network concepts assumes availability of complete communications network resource utilization statistics, and does not concern itself with: performing communications network resource utilization measurements, generating resource utilization statistics, conveying resource utilization statistics, nor with conveying SLA conformance reports in a communications network. As traffic measurement and reporting are current topics of research, the assumptions remain unfulfilled. Nevertheless, if raw traffic measurements were to be supplied in accordance with the RTFM initiative, a large bandwidth overhead and a large processing overhead would be incurred in conveying measurement reports to fulfill the assumptions.
Communications network (service provider/backbone) operators are looking for ways to monitor traffic patterns in real-time, assess service provider/backbone communications network conformance to SLA agreements, towards: enforcing SLA agreed-upon service provisioning characteristics, re-negotiating SLAs, and/or to re-configuring, and ultimately to re-deploying, the communications network infrastructure to support current and planed customer communication network resource utilization needs.
SLA conformance assessments are particularly important in conveying content in accordance with best-effort transport disciplines in non-deterministic packet switching communications networks such as Internet Protocol (IP) networks. Although connection-oriented/deterministic packet switching networks exist, such as Asynchronous Transfer Mode (ATM) networks which only establish end-to-end connections in accordance with pre-defined content transport parameters, assessing conformance to SLA agreements is also important for connection-oriented/deterministic packet switching communications networks as, typically, reserved resources are often over-provisioned, and therefore the available resources being less than optimally employed.
There therefore is a need to solve the above mentioned issues.